Impoverished Howard Tyler decides to move his pregnant wife Judy and their young son Tommy from Massachusetts to the friendly town of Santa Sierra, California, to find his fortune working in the mines. Once there, however, Howard cannot find a job and the family's poverty deepens to the point where Judy cannot even afford a doctor to monitor her pregnancy. In his desperation, Howard meets a petty thief named Jerry Slocum and is easily convinced to work for him, helping him to commit a series of robberies. Convinced that the town is experiencing an incipient crime wave, publisher and editor of the Santa Sierra Journal Hal Clendenning assigns featured columnist Gil Stanton to sensationalize the new trend. Gil's friend, Italian scientist Dr. Vido Simone, who worked on early atomic experiments after Gil helped rescue him from the Nazis in occupied Italy, disapproves of Gil's articles, which he feels may encourage citizens to become vigilantes. Meanwhile, Howard uses the money that he has stolen to provide for his wife and son as he has never been able to do before, but despises himself more and more with each job. When Jerry suggests that they make a big score by kidnapping Donald E. Miller, scion of the city's richest family, Howard agrees, planning to make this crime his last. During the kidnapping, Jerry panics when part of their plan is foiled and decides to murder Donald with a boulder. Revolted by Jerry's brutality, Howard tries to grab the boulder from him, but in a psychotic fit, Jerry smashes Donald's skull, takes his tie pin, and throws his body into the lake. The next day, Jerry decides to continue the kidnapping plan by mailing a ransom note and Miller's tie pin from a neighboring town. He brings along Howard and two women, Hazel Weatherman and Velma, so they will not look suspicious. Hazel, a naïve manicurist who admires Velma's ability to pick up men, instantly decides that she wants Howard, whom she believes is unmarried, even though he is so preoccupied with his own guilt that he pays no attention to her. During the evening, Howard mails the letter, without the tie pin, which he has lost. Later, feeling he cannot face Judy, he shows up drunk at Hazel's doorstep, causing her to assume that he cares for her. When the newspaper arrives, Hazel reads aloud about the murder, and is surprised when Howard reacts violently. As she tries to put him to bed, she discovers the tie pin in his pants cuff, and Howard breaks down and confesses his part in the crime. Seeing her horror, Howard chokes her in a momentary rage, but she breaks away and calls the police. Two days later, while Judy is in a panic over Howard's disappearance, the police arrive at the Tyler house and discover him hiding in the shed. After Howard's arrest, Dr. Simone criticizes Gil for sensationalizing the murder in his articles and making it more difficult for Howard and Jerry to get a fair trial. Although he theorizes that violence is a result of social ills, not human cruelty, Gil is unmoved until Judy visits and reads a touching letter in which a repentant Howard recounts his involvement in the crime and begs her to forget him. Later, Gil visits city hall, where Sheriff Lem Demig also criticizes him for provoking the townspeople. After a lynch mob gathers, Gil admits to himself that if Howard and Jerry now die, he will be directly responsible for it. As Demig removes all other prisoners from the jail to protect them, Gil confronts Howard, who forgives the writer and asks him to care for Judy and Tommy. Efforts to halt the lynching are futile, and the mob storms the prison, drags Howard and Jerry from their cells and hangs them from a nearby tree. Sometime later, Gil tells Demig that he will never forget his part in the horror, and will never let the people forget what they have done.